Solvent-controlled intramolecular [2 + 2] photocycloadditions of alpha-substituted enones.
Solvent-controlled intramolecular [2 + 2] photocycloadditions of alpha-substituted enones.
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α-取代烯酮的溶剂控制分子内 [2 2] 光环加成。
DOI：
10.1021/ja060968g
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发表时间：
2006
影响因子：
15
通讯作者：
Snapper,MarcL
中科院分区：
文献类型：
--
作者：
Ng,StephanieM;Bader,ScottJ;Snapper,MarcL
2‘-羟基烯酮分子内[2+2]光环加成反应的区域选择性和立体选择性与溶剂有关。在非质子性溶剂存在下，2‘-羟基烯酮发生光环加成反应，其方式与分子内氢键的存在相一致。在质子型溶剂中，分子间的相互作用似乎破坏了分子内的氢键，为产物提供了互补的非对映选择性。如果α连接的烯烃的表面可及性受到限制，则环加成反应将根据所用溶剂的性质进行头尾或头尾区域异构体的生成。
The regio- and stereoselectivity of intramolecular [2 + 2] photocycloadditions of 2‘-hydroxyenones are shown to be solvent-dependent. In the presence of aprotic solvents, 2‘-hydroxyenones undergo photocycloadditions in a manner consistent with the presence of an intramolecular hydrogen bond between the carbonyl group and the tether's hydroxy functionality. In protic solvents, intermolecular interactions appear to disrupt the intramolecular hydrogen bond, providing products with complementary diastereoselectivity. If the facial accessibility of the α-tethered olefin is limited, the cycloadditions proceed to give head-to-tail or head-to-head regioisomers, depending on the nature of the solvent employed.